1. Field of the Invention
The present invention relates generally to a fiber reinforced metal composition. More specifically, the invention relates to a method for producing a fiber reinforced metal composition utilizing a fabricated fiber assembly. Further particularly, the invention relates to a method for producing a fiber reinforced metal composition, which method can be implemented without limitation by kind of fabricated fiber assembly and/or metal matrix, volume density of the fiber assembly.
2. Description of the Background Art
Japanese Patent Second (examined) Publication (Tokko) Showa 54-36138 discloses a method for producing a fiber reinforced metal composition, in which fiber of inorganic material is fabricated into a sheet. A molten metal matrix is consolidated with the fiber sheet to form a sheet form fiber reinforced metal composition. For implementing consolidation of the molten metal with the fiber sheet, pressure is exerted on the molten metal, which pressure is adjusted according to an encapsuling program. In the encapsuling program, the pressure to be exerted on the molten metal is first set at 35.2 Kg/cm.sup.2 (500 pounds/inch.sup.2) for pressurization for 0.2 seconds, is subsequently increased to 0.9 tons/6.45 cm.sup.2 (2,000 pounds/inch.sup.2) and further increased to 3 tons/6.45 cm.sup.2.
On the other hand, Japanese Patent Second (examined) Publication (Tokko) Showa 53-12446 discloses a method for producing a fiber reinforced metal composition utilizing a fabricated fiber assembly formed into a desired configuration and consolidated with a metal matrix. During the process of consolidation, the pressure to be exerted on the molten metal is at first set at relatively low pressure and increased moderately, and thereafter increased rapidly to the maximum pressure. The pressure is maintained at the maximum pressure for a given period of time.
In the former case, a plurality plies of fiber sheets are piled or arranged for forming a desired configuration. A difficulty is encountered when a complex configuration of metal composition product, such as a piston is to be formed. Furthermore, discontinuities of fibers between the sheets may cause differences in the strength. Furthermore, by rapidly increasing the pressure to be exerted on the molten metal after a substantially short period in which relatively low pressure is exerted, a blow hole tends to be formed in the product.
In the later case, the following drawbacks are encountered:
(1) when volume density of the fiber assembly is relatively low, the assembly tends to be compressed to reduce the size to change volume density of the fiber assembly; and PA0 (2) when the volume density of the fiber assembly is in excess of 0.6 g/cm.sup.3, resistance against the molten metal entering into the clearance between the fibers becomes excessive causing an increase in the pressure in the molten metal that degrades the quality of the final product.
Therefore, as will be appreciated herefrom, the prior proposed methods limit the configurations of the fiber reinforced composition to be formed and the kinds of fiber and/or metal matrix to be used.